Method and apparatus to decrease the risk of intraneuronal injection during administration of nerve block anesthesia

ABSTRACT

An objective and reproducible system for, and method of, monitoring and/or controlling the pressure during nerve blockage injection, especially by less experienced personnel, is provided in order to decrease the possibility of intraneuronal injection. More specifically, the present invention employs a pressure sensing and/or limiting device located between an injection device (typically a syringe) and a nerve block needle whereby injection pressure during a nerve block injection can be easily and objectively monitored, thereby allowing the operator to monitor the injection pressure and/or injection speed during a nerve blockage injection procedure and to take appropriate corrective actions if abnormal pressure conditions are observed.

TECHNICAL FIELD

[0001] The present invention relates generally to administration ofregional or local anesthesia to achieve peripheral nerve blockade, suchas is useful when a surgeon operates on a patient's arm or leg or totreat pain emanating in the said or other body parts. More particularly,the present invention relates to an improved method and system of localanesthetic administration that includes a device for indicatingpressures interposed between the syringe with local anesthetic andneedle for locating the nerves during administration of nerve blocks.Additionally, since the pressure during nerve block injection alsodepend on the speed of injection, the same device can be used toindirectly monitor and limit the excessive speed of injection

BACKGROUND OF THE INVENTION

[0002] When a surgeon operates on the legs or arms, nerve blockanesthesia may be performed to numb or anesthetize the nervesinnervating the region being operated upon. Performance of nerve blocksconsists of several phases. In the first phase, the operator inserts theneedle in the presumed vicinity of the nerve(s) to be blocked. In doingso, the operator may insert the needle “blindly” relying on anatomicallandmarks, the operator may try to elicit “paresthesia,” whereby thenerve is touched by the needle and the patient perceives “a shock”traveling down the nerve being touched, or the operator may use a nervestimulator to elicit the motor response (twitch) of the nerve beingsought. Whichever method is used, the operator hopes to be in theimmediate vicinity to the nerve (which is necessary for reliable nerveblocks) and not in the nerve itself (which may result in traumatic nerveinjury when the local anesthetic is injected into the nerve). It isimportant to emphasize that all three methods used to locate nerves atbest approximate the needle position in relationship to the nerve andnot confirm it with absolute accuracy. Consequently, with these threedescribed methods for localizing nerves during nerve blocks, the needletip may inadvertently be inserted into the nerve itself. The resultantinjection directly into the nerve(s) may result in significant nerveinjury.

[0003] Regional anesthesia is widely thought to have a number ofadvantages over general anesthesia. Regional anesthesia is an effective,low-cost technique that provides a means of selectively anesthetizing aregion of the body while minimally interfering with the patient's vitalsystems. However, one of the major disadvantages of regional anesthesiaand nerve blocks in particular is the possibility of nerve damage duringadministration of nerve blocks or regional anesthesia. Other drawbacksinclude the risks of systemic and local toxic complications. The primarytarget for local anesthetic effect in regional anesthesia is neuraltissue, such as peripheral nerves, nerve roots, and spinal cord. Thus,it may not be surprising that the most common and troublesome localcomplications of nerve blocks and regional anesthesia involve theperipheral nerves. Such complications are, fortunately, rare, but theycan cause considerable problems for both patient and physician. Of note,even the most careful anesthesiologist will occasionally encounter a PNScomplication. For instance, in a survey of hand surgeons regardingexperience of neurologic complications associated with axillary blockanesthesia, 171 (21%) of the responding 800 surgeons had seen a total of249 major complications (i.e., lasting at least a year), and 521 (65%)had dealt with minor neurologic sequelae (Stark, “Neurologic Injury fromAxillary Block Anesthesia,” J. Hand Surg. 21A, 391 (1996)). Thus, aboutone of five hand surgeons has seen a major neurologic sequela that mighthave been related to a nerve block. While the overall incidence of nervedamage after nerve blocks is relatively low, the consequences can becatastrophic and result in a temporary or permanent injury to the nerve,loss of limb function and paralysis. See, e.g., Auroy et al., “SeriousComplications Related to Regional Anesthesia: Results of a ProspectiveSurvey in France,” Anesthesiology, 87, 479-484 (1997); Eisenach,“Regional Anesthesia: Vintage Bordeaux (And Napa Valley),”Anesthesiology, 87, 467-9 (1997). Indeed, the neurologic complicationsafter regional anesthesia are among the most commonly discussed issuesat various anesthesia conferences, and a common topic of many scientificpublications. Lesions to the brachial plexus seem to be reported mostfrequently. See, e.g., Bonica et al., “Brachial Plexus BlockAnesthesia,” Am. J. Surg., 78, 65 (1949); Moberg et al., “BrachialPlexus Block Analgesia with Xylocaine,” J. Bone Joint Surg., 33A, 884(1951); Wolley et al., “Neurological sequelae of brachial plexus nerveblock,” Ann. Surg., 149, 53 (1959); Brand et al., “A Comparison ofSupraclavicular and Axillary Techniques for Brachial Plexus Blocks,”Anesthesiology, 22, 226 (1961); Schmidt et al., “Komplikationen undGefahren der Plexus-brachialis-Anesthesie unter besondererBerucksictinung von Langzeitschaden,” Anasth. Intensivther. Notfallmed.,16, 346 (1981); de Jong, “Axillary block of the brachial plexus,”Anesthesiology, 22, 215 (1961); Hamelberg et al., “Perivascular AxillaryVersus Supraclavicular Brachial Plexus Block and General Anesthesia,”Anesth. Analg., 41, 85 (1962); Wall, “Axillary nerve blocks,” Ann.Surg., 149, 53 (1959); Moore et al,. “Bupivacaine: a Review of 11,080Cases,” Anesth. Analg., 57, 42 (1978); Selander et al., “Parasthesiae orNo Parasthesiae ? Nerve Lesions after Axillary Blocks,” Acta. Anaesth.Scand., 23, 27 (1979); Plevak et al., “Paresthesia Vs. NonParesthesia—the Axillary Block,” Anesthesiology, 59, A216 (1983);Winchell et al., “The incidence of neuropathy following upper extremitynerve blocks,” Reg. Anesth., 10, 12 (1985); Tourtier et al.,“Complications of Axillary Block Using Two Techniques: Experience with1400 Cases,” Anesthesiology, 71, A726 (1989); Davis et al., “BrachialPlexus Anesthesia for Outpatient Surgical Procedures on an UpperExtremity,” Mayo Clin. Proc., 66, 470 (1991); Stan et al., “TheIncidence of Neurovascular Complications Following Axillary BrachialPlexus Block Using a Transarterial Approach,” Reg. Anesth., 20, 486(1995); Lofstrom et al., “Late Disturbances in Nerve Function afterBlock with Local Anesthetic Agents.” Acta. Anesth. Scand., 10, 111(1966); Mogensen et al., “Posttraumatic Instability of theMetacarpophalangeal Joint of the Thumb,” Hand, 12, 85(1980).

[0004] One of the mechanisms of nerve injury is inadvertent insertion ofthe needle into a nerve with consequent injection of local anestheticinside the nerve. This in turn may result in either mechanical trauma tothe nerve, ischemic injury to the nerve due the resultant increase inendoneural pressure due to the high pressures inside the nerve, and/orendoneral edema. Indeed, experimentally, it was found thatintrafascicular injections in rabbit sciatic nerve in vivo can produceendoneural pressures of more than 700 mm Hg, and after such injectionsthe endoneural pressure could exceed the estimated capillary perfusionpressure for about 15 minutes. During this period, the nerve fascicle isboth ischemic and vulnerable to otherwise toxicologically neutral localanesthetic solutions. Selander et al., “Longitudal Spread ofIntraneurally Injected Local Anesthetics,” Acta Anesth. Scand., 22, 622(1978). Similar conditions can also occur in humans, and admixture ofepinephrine with local anesthetic can enhance ischemia when injectedintraneuronally and thus increase the risk of nerve injury. Selander etal., “Parasthesiae or No Parasthesiae ? Nerve Lesions after AxillaryBlocks,” Acta Anaesth. Scand., 23, 27 (1979). The pressures on normalinjection of local anesthetics in humans range from about 500 mm Hg toabout 1200 mm Hg. Higher pressures may indicate an intraneuronalinjection. Hadzic et al., “Injection Pressure During Peripheral NerveBlockade,” Anesthesiology, Abstract (2002).

[0005] The current recommendations to decrease the risk ofintra-neuronal injections consist of slow injection to avoid highinjection pressures and the avoidance of injection when high pressuresare noticed during injection of local anesthetic. Finucane,Complications of Regional Anesthesia, Churchill Livingstone, N.Y.(1999). However, these recommendations assume that the operator oroperators are able to perceive the difference between “normal” and“abnormal” injection pressures and take appropriate actions when“abnormal” injection pressures are observed. However, these judgmentsare prone to subjective interpretation and/or the “feel” of theoperators and not on any objective measurements (e.g., measuredinjection pressure, speed, or similar variables). The ability ofdifferent operators to estimate and/or control the injection (especiallyas with regard to pressure) is further complicated by differences inhand strength and experience among operators as well as differences inresistance to injection for various needle types, lengths, and lumencalibers. In addition, in clinical practice, it is common practice foran operator (e.g., anesthesiologist, nurse anesthesiologist, otheranesthesia providers, and the like) to perform the needle placement withan assistant (often without significant experience in nerve blockade)who injects the local anesthetic. This practice poses a risk of exertingtoo high pressures during injection and possible unrecognizedintraneuronal injection. In addition, the operator typically uses bothhands to perform the procedure (i.e., place the injection needle in theappropriate location relative to the nerve) and cannot easily determineand/or control the amount of force and pressure that the assistant mayemploy to inject the local anesthetic.

[0006] Moreover, forceful and/or fast injections of local anestheticsolutions can lead to a higher risk of systemic local anesthetictoxicity (e.g., seizures, arrhythmia, cardiovascular collapse, anddeath) due to tracking of local anesthetic between tissue layers andinadvertent intravascular injections. Additionally, intraneuronal andrapid injections of local anesthetics can backtrack to the spinal columnand result in unintended epidural or spinal anesthesia with potentiallydisastrous consequences (Selander et al., “Longitudal Spread ofIntraneurally Injected Local Anesthetics,” Acta Anesth. Scand., 22, 622(1978); Tetzlaff et al., “Subdural Anesthesia as a Complication of anInterscalene Brachial Plexus Block,” Regional Anesthesia, 19, 357-359(1994); Dutton et al., “Total Spinal Anesthesia after InterscaleneBlockade of the Brachial Plexus,” Anesthesiology, 80, 939-941 (1994)).

[0007] Various attempts have been made to improve anesthesiainstruments. See, e.g., U.S. Pat. No. 5,119,832 (Jun. 9, 1992); U.S.Pat. No. 5,378,241 (Jan. 3, 1995); U.S. Pat. No. 4,994,036 (Feb. 19,1991); U.S. Pat. No. 4,775,367 (Oct. 4, 1988); U.S. Pat. No. 4,889,529(Dec. 26, 1989); U.S. Pat. No. 4,917,670 (Apr. 17, 1990); U.S. Pat. No.4,917,668 (Apr. 17, 1990); U.S. Pat. No. 5,085,631 (Feb. 4, 1992); U.S.Pat. No. 5,106,376 (Apr. 21, 1992); U.S. Pat. No. 5,135,525 (Aug. 4,1992); U.S. Pat. No. 5,312,374 (May 17, 1994); U.S. Pat. No. 5,328,479(Jul. 12, 1994); U.S. Pat. No. 5,512,052 (Apr. 30, 1996); U.S. Pat. No.5,630,802 (May 20, 1997). None of these attempts, however, focused oncontrolling and/or measuring the pressure and/or injection speed duringinjection to avoid an inadvertent intraneuronal injection, or rapidspread, and/or absorption of local anesthetics during nerveblockade/regional anesthesia.

[0008] Thus, it is clear that a more objective and reproducible methodof monitoring and/or controlling the pressure and/or injection speedduring nerve blockage injection, especially by less experiencedpersonnel and/or assistants, would be beneficial in order to decreasethe possibility of intraneuronal injection. The present inventionprovides such a method and apparatus.

SUMMARY OF THE INVENTION

[0009] The present invention provides an objective and reproduciblemethod of monitoring and/or controlling the pressure during nerveblockage injection, especially by less experienced personnel and/orassistants, in order to decrease the possibility of intraneuronalinjection. More specifically, the present invention employs a pressuresensing and/or limiting device located between an injection device(typically a syringe) and a nerve block needle whereby injectionpressure during a nerve block injection can be easily and objectivelymonitored, thereby allowing the operator to monitor the injectionpressure during a nerve blockage injection procedure. Additionally,since the pressure during nerve block injection also depend on the speedof injection, the same device can be used to indirectly monitor andlimit excessive injection speeds.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010]FIG. 1 illustrates one embodiment of the nerve blockage injectionsystem of the present invention.

[0011]FIG. 2 illustrates one embodiment of the pressure sensing deviceused in the present invention. Panel A provides a side view of thepressure sensing device indicating “low” or “normal” pressure. Panel Bprovides the same side view except that the pressure sensing deviceindicates “high” or “abnormal” pressure. Panel C provides a top view ofthe pressure sensing device.

[0012]FIG. 3 provides a flowchart illustrate the general method of thepresent invention.

[0013]FIG. 4 provides a flowchart illustrating one preferred embodimentof the general method of the present invention wherein ananesthesiologist or other health care provider employs an assistant tooperate the injection device.

DETAILED DESCRIPTION OF THE INVENTION

[0014] The present invention provides an objective and reproduciblemethod of monitoring and/or controlling the pressure during nerveblockage injection, especially by less experienced personnel, in orderto decrease the possibility of intraneuronal injection. Morespecifically, the present invention employs a pressure sensing and/orlimiting device located between an injection device (typically asyringe) and a nerve block needle whereby injection pressure during anerve block injection can be easily and objectively monitored, therebyallowing the operator to monitor the injection pressure during a nerveblockage injection procedure.

[0015] For purposes of this invention, the terms “local,” “regional,”and “nerve block” with respect to anesthesia are intended to besynonymous and interchangeable. For purposes of this invention, a“normal” injection pressure is generally considered to be in the rangeof the typical pressure normally encountered in a particular type ofnerve bock procedure. An “abnormal” injection pressure is generallyconsidered to be above the range of such typical pressures normallyencountered in a particular type of nerve bock procedure. And, ofcourse, an “intermediate” injection pressure would span the higher endof the “normal” pressure range and the lower end of the “abnormal”range. For guidance purposes only, a normal injection pressure wouldgenerally be less than about 15 psi; an intermediate injection pressuregenerally would be about 15 to about 25 psi; and an abnormal injectionpressure would generally be greater than about 25 psi. Of course, thesepressures may vary depending on the patient, the type or location of thenerve block, the type, length, or caliber of the needle, thecomposition, viscosity, or other characteristics of the anesthetic used,speed or force of the injection, as well as other factors.

[0016] The present apparatus for performing a nerve block injectioncomprises an anesthetic delivery device (e.g., syringe) having ananesthetic storage compartment and an output end, an anesthetic needleor catheter having an input end and an output end, an anestheticpassageway connecting the output end of the anesthetic delivery deviceand the input end of the anaesthetic needle whereby anesthetic from theanesthetic storage compartment can be delivered via the output end ofthe anesthetic needle to a patient, and a pressure sensing devicelocated along, and in pressure sensing communication with, theanesthetic passageway, whereby the pressure of the anesthetic can bemonitored during the nerve block injection.

[0017] One embodiment of the present invention is shown in FIG. 1 havingan anesthetic delivery device 10, a pressure indicating device 20,flexible tubing 52, and a needle 60 for delivering anesthetic adjacentor in the vicinity of nerve 72 for which a nerve block is desired. Theanesthetic delivery device 10 shown in FIG. 1 is a syringe having a body18, an anesthetic storage compartment 12, a movable piston 16, and anoutput end 14. Other suitable anesthetic delivery devices include, forexample, mechanical pumps, and the like so long as they can becontrolled by an operator. The output end 14 is adapted to be fitted orattached to the pressure indicating device 20 at its input end 22. Theoutput end 26 is attached via flexible tubing 52 (having an input end 50and an output end 52). The output end 54 of the flexible tubing 52 isattached to the input end 62 of needle 60. Needle 60 has an output end64 for delivering anesthetic to a desired location. In operation, as thepiston 16 is depressed, anesthetic flows from the anesthetic storagecompartment 12, through the pressure indicating device 20 (viapassageway 38), through flexible tubing 52, and through needle 60 inorder to be injected at the desired location to effect the nerve block.

[0018] Although the pressure indicating device 20 shown in FIG. 1 isattached directly to the output end 22 of syringe 10, it could beattached via flexible tubing (similar to flexible tubing 52) so that itcould be located anywhere along the length of flexible tubing 52(including directly attached to the input end 62 of needle 60) asdesired. Such a pressure sensing/monitoring device 20 could also bebuilt-in into the syringe-piston mechanism and/or the needle device,rather than being attached to the syringe as shown in FIG. 1.Additionally, more than one pressure indicating device 20 could beincluded if desired. For example, one pressure indicating device 20could be located near the output end 22 of syringe 10 and another onenear the input end 62 of needle 60 to allow observation of the injectionpressure by an operator controlling the needle 60 (e.g.,anesthesiologist, nurse anesthesiologist, other anesthesia providers,and the like) and an assistant controlling the syringe 10.

[0019] One embodiment of the pressure indicating device 20 is shown inmore detail in FIG. 2 wherein the device in Panel A illustrates a normalpressure condition and Panel B illustrates an abnormal or high pressurecondition. The pressure indicating device 20 is formed in a body 24 withan input end 22 to receive anesthetic from the anesthetic deliverydevice 10, a passageway 38 allowing anesthetic to pass through the body24, and an output end 26 to deliver anesthetic to the needle 60 viaflexible tubing 52. The body has an internal flexible membrane 36 withinpressure expansion chamber 32 such that as the injection pressure of theanesthetic increase, the membrane 36 can expand within the pressureexpansion chamber 32 as shown in Panel B thereby forcing pressureindicating pin 28 to extend beyond a top housing 30 to indicate theinjection pressure. As shown in Panel B, the passageway 38 is in fluidcommunication with the membrane 36 via passageway opening 40. Panels Aand B provide side views; Panel C provides a top view. Although membrane36 is shown as circular in Panel C, it could be of any shape so long asit can be expanded sufficiently to move the pressure indicating pin 28to indicate increase injection pressure. Preferably, membrane 26 isconstruction of flexible silicone, flexible polyurethane, flexiblerubber, or other flexible materials suitable for use in medical devices.

[0020] As the injection pressure increases, anesthetic can force themembrane 36 to expand and thereby enter into portion 42 of the expansionchamber 32 and move the pressure indicating pin 28 upward and out of thetop housing 30. With increased pressure, a larger volume of localanesthetic within portion 42 expands or stretches membrane 36 and allowsthe volume within portion 42 to increase and move the pressureindicating pin 28. The top housing 30 is used to keep the pressureindicating pin 28 in proper alinement so that it can move, depending onthe injection pressure, from and to the positions illustrated in PanelsA and B. The pressure indicated pin 28 has an associated spring 34 toresist movement upward. The strength of the spring 28 can be selected toprovide the desired resistant to movement and, therefore, the range ofpressures required to move the pressure indicated pin 28. The extend ofexpansion of the membrane (and thus the relative size or volume ofportion 42 and the extent of travel of pressure indicating pin 28) willdepend on the injection pressure and/or injection speed.

[0021] As shown in Panels A and B, the pressure indicating pin 28 iscolor coded to indicate relative injection pressure. In the embodimentindicated, green would indicate normal injection pressure, yellow wouldindicate an intermediate pressure, and red would indicate an abnormallyhigh pressure. The color exposed on the pressure indicating pin 28would, therefore, provide a quick and visual indication of the injectionpressure along with an indication of how to proceed with the injection.Thus, for example, green (i.e., normal pressure) would indicatecontinuing the injection procedure; yellow (i.e., intermediate pressure)would indicate the injection could be continued but that the pressureshould be monitored carefully; and red (i.e., abnormal pressure) wouldindicate that the injection should be terminated until with cause of thehigh pressure is identified. Of course, other color coding or othercoding systems can be used if desired so long as the changes in pressureduring injection can be easily monitored. In operation, during normalinjection pressures, the pressure indicating pin 28 would remain in theretracted position as shown in Panel A with only green showing. Duringabnormal injection pressure, the pressure indicating pin 28 would moveto its extended position as shown in Panel B with red now showing toindicate the abnormal pressure; when the injection pressure decreases,the pressure indicating pin 28 would then move downward to, once normalinjection pressures are reestablished, to the position shown in Panel A.

[0022] Generally, a normal injection pressure (i.e., the green positionin FIG. 2) would be less than about 15 psi; an intermediate injectionpressure (i.e., the yellow position in FIG. 2) would be about 15 toabout 25 psi; and an abnormal injection pressure (i.e., the red positionin FIG. 2) would be greater than about 25 psi. Of course, thesepressures may vary depending on the patient, the type or location of thenerve block, the type, length, or caliber of the needle, thecomposition, viscosity, or other characteristics of the anesthetic used,speed or force of the injection, as well as other factors. Thus,pressure indicating devices having different operating pressure rangesmay be provided so that the operator can selected the appropriate rangefor the specific application and/or patient.

[0023] Generally conventional materials of construction normally used inmedical devices can be used to form the pressure indicating device 20.Of course, all materials contacting the anesthetic (e.g., the interiorof passageway 38, membrane 36, and portion 42 of expansion chamber 32)should be inert relative to the anesthetic. Additionally, all materialsof construction should be capable of being rendered medical sterileusing conventional procedures. It is generally preferred, thatlightweight plastic materials be used whenever possible. It is alsogenerally preferred that the pressure indicating device 20 is used onceand discarded using appropriate procedures. If desired, however, thematerials of construction for pressure indicating device 20 can beselected such that it can be resterilized for multiple usage.

[0024] In operation, the operator (e.g., anesthesiologist, nurseanesthesiologist, other anesthesia providers, and the like) inserts theneedle 60 into the patient through the skin 70 such that the needle tip64 can deliver anesthetic adjacent, near, or in the immediate vicinityof the nerve 72 to be anesthetized. Conventional techniques are used toposition the needle tip 64 in the desired location relative to the nerve72. Once the needle 60 and needle tip 64 are appropriately placed, thelocal anesthetic is injected by exerting the pressure on the piston 16of the syringe 10. The operator or an assistant observes the pressureindicating device 20 during injection so that, if the pressureincreases, the appropriate action (as determined by the operator) can beundertaken.

[0025] During nerve block injection, higher than desired pressures(i.e., intermediate or abnormal pressure) can occur due to a too fastinjection of local anesthetic, obstruction of the needle tip due totissue debris, or inadvertent placement of the needle inside the nerve.The operator upon observing increased pressure normally wish todetermine the cause of the increased pressure in determining how toproceed. In the event of higher than normal pressures, the operator hasthe option to disregard the data and continue the injection, slow therate of injection, or to stop injection and reposition and/or flush theneedle and then continue the injection.

[0026] The general procedure for using the apparatus of the presentinvention is illustrated in FIG. 3. To begin the nerve block, the nerveblock needle is inserted into the patent at the appropriate location(i.e., in the immediate vicinity of the nerve to be blocked). Afterconfirming that the location is acceptable using conventional techniques(e.g., using anatomical landmarks, achieving paresthesia (sensationtraveling in the are of the nerve to be blocked distribution), and/orobtaining motor stimulation (muscle twitch) using a nerve stimulator),the injection is begun. The injection pressure during injection ismonitored using the pressure sensing device. The injection is continued,modified, or terminated depending on the injection pressure observed.For example, if only normal or acceptable pressure are observed duringthe injection, the injection is continued until completion. If however,higher than normal pressure are observed, the injection may be modifiedor terminated as appropriate. The method of the present invention may becarried out by a single individual (e.g., anesthesiologist, nurseanesthesiologist, other anesthesia providers, and the like) or by suchan individual using an assistant.

[0027] A preferred procedure for using the apparatus of the presentinvention is illustrated in FIG. 4 wherein the operator who positionsthe needle relative to the nerve to be block uses an assistant tooperate the anesthetic delivery device and observe the pressureindicating device. In FIG. 4, the actions of the anesthesiologist (orother health care provider) and the assistant are generally presented onthe left and right sides, respectively. To begin the nerve block, theanesthesiologist inserts the nerve block needle into the patent at theappropriate location (i.e., in the immediate vicinity of the nerve to beblocked). After confirming that the location is acceptable usingconventional techniques (e.g., using anatomical landmarks, achievingparesthesia (sensation traveling in the are of the nerve to be blockeddistribution), and/or obtaining motor stimulation (muscle twitch) usinga nerve stimulator), the anesthesiologist instructs the assistant tobegin the injection. The assistant then begins the injection andcontinuously monitors the pressure sensing device. If only normal oracceptable pressure are observed during the injection, the injection iscontinued until completion. If, however, intermediately or abnormallyhigh pressure are observed, the assistant informs the anesthesiologistwho must make a decision as whether to interrupt or continue theinjection. If the pressure is only in the intermediate level (i.e.,yellow showing on the pressure indicating pin 28 (see FIG. 2)), theanesthesiologist may wish to continue the injection unless abnormalpressures are later observed. Whether in the intermediate or abnormallevel, the anesthesiologist may instruct the assistant to stop orinterrupt the injection so that corrective action may be undertaken.Such corrective action may include, for example, repositioning theneedle relative to the nerve, clearing the needle tip of debris that mayhave blocked the needle, allowing the pressure to decrease beforerestarting the injection, reducing the speed of the injection,terminating the injection in order to start over, and the like. Once theanesthesiologist has completed the necessary corrective actions (except,of course, terminating the injection), instructions are given to theassistant to restart the injection. Upon restarting the injection, theassistant will again monitor the injection pressure as described aboveand providing the necessary information should the pressure increase tointermediate or abnormal levels again.

[0028] Although the assistant both monitors the pressure sensing deviceand operates the syringe or other pumping device in the methodillustrated in FIG. 4, the anesthesiologist or other health careprovider may also be involved in these activities. For example, thepressure sensing device could be located at a position near the needle(as opposed to near the syringe) to allow the anesthesiologist or otherhealth care provider to easily monitor the injection pressure duringinjection as well as control the needle position. Alternatively, theanesthesiologist or other health care provider could practice the methodof the present invention without the use of an assistant. In such acase, the syringe or other pumping device could preferably be operatedby a foot peddle or other device to leave the operator's hand free toplace and control the needle.

[0029] The present method provides the anesthesiologist the option ofcontinuing the injection even if intermediate or abnormal pressures areobserved based on his or her best medical judgement. In such cases, theanesthesiologist will instruct the assistant to continue the injection.Even in such cases, the assistant preferably should continue to monitorthe injection pressure in case it increases dramatically so that, ifappropriate, the anesthesiologist can reconsider the decision tocontinue. Generally, high pressures due to a intraneuronal injection aremost commonly observed at the beginning of the injection; however, theneedle be initially placed outside the nerve and then inadvertentlyadvanced into the nerve during the injection, resulting in higherpressures.

[0030] If desired, the pressure sensing device may also be equipped witha pressure-activated shut-off so that if the injection pressure reachessome predetermined level, flow of the anesthetic will be automaticallystopped. Although this predetermined level may be set at any level, itis generally preferred that it be set at a level at or near the abnormalpressure range (e.g., generally at a level of about 25 psi or higher).This automatic shut-off feature may also, if desired, be equipped with amanual override mechanism so that the anesthesiologist, if desired, cancontinue the injection with or without corrective actions. It willgenerally be preferred, however, that such an injection not be continuedunless such corrective actions are successfully undertaken.

[0031] Of course, those skilled in the art may use other, similarmechanisms to measure and/or determine the pressures during nerve blockinjection and that various details of the invention may be changedwithout departing from the scope of the invention. All references citedherein are hereby incorporated by reference. Furthermore, the foregoingdescription is for the purpose of illustration only, and not for thepurpose of limitation, which is defined in the following claims.

What is claimed is:
 1. A system for administration of a nerve block in apatient with reduced risk of intraneuronal injection, said systemcomprising (1) an anesthetic delivery device having an anestheticstorage compartment and an output end; (2) an anesthetic delivery devicehaving an input end and an output end wherein the output end can beinserted into the patient for delivery of anesthetic to the patent inthe vicinity of a nerve to be blocked; (3) a tube having an anestheticpassageway connecting the output end of the anesthetic delivery deviceand the input end of the anaesthetic delivery device, whereby anestheticfrom the anesthetic storage compartment can be delivered via the outputend of the anesthetic delivery device to the patient; and (4) a pressuresensing device located along, and in pressure sensing communicationwith, the anesthetic passageway, whereby the pressure of the anestheticcan be monitored during anesthetic delivery to the patient so as toreduce the risk of intraneuronal injection.
 2. The system as defined inclaim 1, wherein the anesthetic delivery device is a syringe.
 3. Thesystem as defined in claim 1, wherein the anesthetic delivery device isa nerve block needle.
 4. The system as defined in claim 2, wherein theanesthetic delivery device is a nerve block needle.
 5. The system asdefined in claim 3, wherein the tube is flexible tubing.
 6. The systemas defined in claim 4, wherein the tube is flexible tubing.
 7. Thesystem as defined in claim 1, wherein the pressure sensing device allowsvisual detection of at least normal and abnormal pressures duringanesthetic delivery to the patient.
 8. The system as defined in claim 2,wherein the pressure sensing device allows visual detection of at leastnormal and abnormal pressures during anesthetic delivery to the patient.9. The system as defined in claim 3, wherein the pressure sensing deviceallows visual detection of at least normal and abnormal pressures duringanesthetic delivery to the patient.
 10. The system as defined in claim4, wherein the pressure sensing device allows visual detection of atleast normal and abnormal pressures during anesthetic delivery to thepatient.
 11. The system as defined in claim 1, wherein the pressuresensing device is further equipped with an automatic shut-off devicewhereby anesthetic delivery is prevented when the pressure of theanesthetic during anesthetic delivery increases above a predeterminedlevel.
 12. The system as defined in claim 6, wherein the pressuresensing device is further equipped with an automatic shut-off devicewhereby anesthetic delivery is prevented when the pressure of theanesthetic during anesthetic delivery increases above a predeterminedlevel.
 13. A method of administering a nerve block to a patient withreduced risk of intraneuronal injection, said method comprising (a)providing a system for administration of the nerve block in the patientwith reduced risk of intraneuronal injection, said system comprising (1)an anesthetic delivery device having an anesthetic storage compartmentand an output end; (2) an anesthetic delivery device having an input endand an output end wherein the output end can be inserted into thepatient for delivery of anesthetic to the patent in the vicinity of anerve to be blocked; (3) a tube having an anesthetic passagewayconnecting the output end of the anesthetic delivery device and theinput end of the anaesthetic delivery device, whereby anesthetic fromthe anesthetic storage compartment can be delivered via the output endof the anesthetic delivery device to the patient; and (4) a pressuresensing device located along, and in pressure sensing communicationwith, the anesthetic passageway, whereby the pressure of the anestheticcan be monitored during anesthetic delivery to the patient so as toreduce the risk of intraneuronal injection; (b) inserting the output endof the anesthetic delivery device into the vicinity of the nerve to beblocked; (c) starting delivery of the anesthetic; (d) monitoring thepressure of the anesthetic during delivery of the anesthetic; (e)continuing delivery of the anesthetic so long as the pressure remainswithin a normal range; (f) if the pressure increases to an abnormalrange, interrupt delivery of the anesthetic so that appropriatecorrective action can be taken; (g) if the delivery of the anesthetic isinterrupted in step (f), take the appropriate corrective action andcontinue delivery of the anesthetic; and (f) repeat steps (d) through(g) until delivery of the anesthetic is complete or delivery ofanestheticfl is terminated.
 14. The method of claim 13, wherein theanesthetic delivery device is a syringe and the anesthetic deliverydevice is a nerve block needle.
 15. The method of claim 13, wherein thetube is flexible tubing.
 16. The method of claim 14, wherein the tube isflexible tubing.
 17. The method of claim 13, wherein the pressuresensing device allows visual detection of at least the normal range andthe abnormal range of pressures during anesthetic delivery to thepatient.
 18. The method of claim 14, wherein the pressure sensing deviceallows visual detection of at least the normal range and the abnormalrange of pressures during anesthetic delivery to the patient.
 19. Themethod of claim 13, wherein an operator and an assistant administer thenerve block to the patient such that the assistant monitors the pressureand reports pressures in the abnormal range so that the operator cantake appropriate corrective action.
 20. The method of claim 14, whereinan operator and an assistant administer the nerve block to the patientsuch that the assistant monitors the pressure and reports pressures inthe abnormal range so that the operator can take appropriate correctiveaction.